The present invention relates to electrodeposited copper foil with carrier; to a method for producing the electrodeposited copper foil; and to a copper-clad laminate formed by use of the electrodeposited copper foil with carrier.
Conventionally, peelable-type electrodeposited copper foils with carrier have been widely employed for producing copper-clad laminates, by laminating the copper foil with a substrate through hot pressing and then peeling off the carrier attached to the electrodeposited copper foil. The peel strength at the release interface between the carrier and the copper foil varies over a wide range. Some electrodeposited copper foils with carriers exhibit easy peeling during handling thereof, and others exhibit failure to peel after hot pressing is carried out.
In order to solve the aforementioned problems, the present inventors have proposed electrodeposited copper foils with carrier in which the release interface between a carrier and a copper foil is formed from an organic agent. A main advantage of the copper foils with carriers is moderate and stable peeling strength at the release interface. The technical idea relating to such electrodeposited copper foils with carrier will enable production of new types of foils which have not yet been developed.
One example is an electrodeposited copper foil with carrier produced by forming an organic release interface on the carrier, forming copper microparticles on the release interface through electrodeposition; and subjecting the thus-coated foil to anti-corrosion treatment. The electrodeposited copper foil with carrier is used for producing printed wiring boards in the following manner.
Firstly, a substrate (prepreg) is laminated onto the electrodeposited copper layer formed of copper microparticles, followed by hot-pressing, to thereby prepare a copper-clad laminate. Thereafter, the carrier is removed from the copper clad laminate.
Subsequently, a bulk copper layer which serves as a conductor of a printed wiring board is formed on the copper-microparticle layer to an arbitrary thickness through copper plating followed by a step; e.g., any etching step, thereby producing a typical printed wiring board as a final product. This sequence would be considerably effective for producing wiring boards that satisfy the demand for more finely patterned wiring boards.
However, when the electrodeposited copper foil layer contained in an electrodeposited copper foil with carrier is formed exclusively from copper microparticles and a release interface is formed from an organic agent, conditions for producing the copper foil with carrier must be carefully controlled. Thus, unless the conditions are appropriate, moderate and stable peel strength is not attained.
In practice, the organic release interface layer formed is damaged during formation of a copper-microparticle layer and during anti-corrosion surface treatment, thereby affecting peeling strength at the interface. This phenomenon has been investigated thoroughly, and the inventors have found that when the amount of an organic material forming the release interface layer decreases, the peel strength at the release interface between the carrier foil layer and the copper-microparticle layer increases thereby worsening peelability.